Copper electrolytic plating bath and copper electrolytic plating method

ABSTRACT

Disclosed herein is a copper electrolytic plating bath including copper sulfate used in an amount of 50 to 250 g/liter calculated as copper sulfate pentahydrate, 20 to 200 g/liter of sulfuric acid, and 20 to 150 mg/liter of a chloride ion, and a sulfur atom-containing organic compound and a nitrogen atom-containing organic compound serving as organic additives. The nitrogen atom-containing organic compound includes a nitrogen atom-containing polymer compound obtained by a two-stage reaction including reacting one mole of morpholine with two moles of epichlorohydrin in an acidic aqueous solution to obtain a reaction product and further reacting one to two moles, relative to one mole of the morpholine, of imidazole with the reaction product.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2009-238460 filed in Japan on Oct. 15, 2009, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a copper electrolytic plating bath and method, which enable high-speed plating to articles to be plated, especially particles having through-holes, blind via holes, or posts.

BACKGROUND ART

In copper electrolytic plating on a flat surface such as of a laminated copper foil on a substrate, high-speed plating has hitherto been conducted by increasing a plating bath temperature and a cathode current density (see Japanese Patent No. 3756852). However, in case of copper electrolytic plating on a substrate having through-holes (TH) or blind via holes (via), speeding-up of the plating is not easy because of the requirements for throwing power (TP: ability of an electrolytic solution to deposit metal in uniform thickness) and physical properties of the deposit (e.g. appearance, tensile strength, elongation percentage and the like).

When a substrate has through-holes or blind via holes whose aspect ratio (AR) is small, high-speed plating is possible by strengthen plating agitation and increasing plating temperature. However, if the aspect ratio becomes large, there arise problems in that the throwing power becomes worsened along with the physical properties of the deposit. Hence, there is limitation on the type of substrate to be plated to which high-speed plating is carried out by strengthening the agitation and increasing plating temperature.

In the conventional copper electrolytic plating baths, plating has been conducted while ensuring the throwing power and the physical properties of the deposit within allowable ranges by increasing the agitation if the plating temperatures is lower than 30° C. and the cathode current density is less than 5 A/dm². However, for further speeding-up by applying a cathode current density of at least 5 A/dm², it is necessary to elevate the plating temperature, since there is a limit for the power-up of agitation. The elevation of the temperature has presented a problem in that the conventional organic additives used for plating a substrate having through-holes and blind via holes lose their effect.

With respect to post plating wherein plating is carried out on a recessed portion formed by a resist film, if the resist film has a low height and large-sized individual openings (i.e. a small aspect ratio), as in the case of blind via holes, the throwing power and the physical properties of the deposit can be ensured with the conventional electrolytic plating baths so long as agitation is strengthened. However, if the aspect ratio becomes large, good plating is not expected even if strong agitation is conducted. Even if plating is performed at high speed by strengthening agitation and increasing a plating temperature, a problem is involved in that the deposit cannot be flattened. At any event, plating on a post (bump) having a large aspect ratio is carried out at high speed, it is necessary to increase the plating temperature. In any of plating substrates having through-holes or blind via holes and plating on posts (bumps), additives suited for high temperature plating should have been needed.

SUMMARY OF INVENTION

The invention has been made under these circumstances in the art and it is an object of the invention to provide a copper electrolytic plating bath which enables high-speed plating on a substrate having through-holes, blind via holes, posts or the like formed therein while keeping good throwing power and ensuring physical properties of the deposit.

It is another object of the invention to provide a copper electrolytic plating bath which contains organic additives effectively acting for the case of high temperatures responsible for high-speed plating.

It is a further object of the invention to provide a copper electrolytic plating method using the above-described copper electrolytic plating bath.

The advantages of the high-speed plating include shortage of plating time and the possibility of increasing a quantity of output per unit time. The quantity of output increases if a takt time can be shortened. Moreover, a plating equipment can be saved in space and the size of a plating equipment can be made smaller for the same quantity of output (e.g. the numbers of lines and plating equipment can be reduced). For instance, if a cathode current density can be doubled, any of a line length, the number of plating tanks, an amount of plating bath and a plating time can be reduced substantially to half. The speeding up of plating is thus important from the standpoint of the reduction of plating costs.

At first, we assume the reasons why high-speed plating substrates having through-holes, blind via holes, etc., has not been conventionally conducted (i.e. problems ascribed to high-speed plating) in the following way.

-   (1) Throwing power of through-holes or blind via holes is worsened,     thus not satisfying the requirement for the high-speed plating. The     post geometry is poorly changed, thus not satisfying the     requirement. -   (2) Physical properties of the deposit are worsened. Especially,     gloss is unsatisfactory. -   (3) When a soluble anode is used, the anode is turned nonconductive.     If a current density is increased at 25° C., a copper concentration     in the vicinity of the anode is made high, under which there is a     tendency that crystals of copper sulfate pentahydrate are deposited     on the anode, thereby rendering the anode nonconductive. -   (4) There are no organic additives, particularly, levelers, which     can be used at high temperatures.

On the other hand, if a plating temperature is made high, the solubility of copper sulfate pentahydrate increases, so that crystallization is unlikely to occur, with the attendant advantage that nonconductiveness is also unlikely to occur.

As a compound usable as a leveler of high-speed copper electrolytic plating baths, studies have been made in order to obtain, as an effective additive, a compound (i) that is able to keep an effect as a leveler when agitation is made strong and a plating temperature is elevated, i.e. a compound that shows high throwing power relative to through-holes and blind via holes and is capable of forming a plated film whose physical properties are good, or a compound capable of flat post (bump) plating.

Additionally, if the effect of either of an promoter or an inhibitor for organic additives is in excess under temperature-elevated conditions, the physical properties of the deposit would be worsened and the throwing power would lower. To avoid this, we have made studies in order to obtain, as an effective additive, a compound that is able to balance a promoter effect and an inhibitor effect attributed to an organic additive contained in a plating bath under plating temperature-elevated conditions.

We have made intensive studies to solve the above problems and, as a result, found that in a copper electrolytic plating bath comprising copper sulfate, sulfuric acid and chloride ions as well as a sulfur atom-containing organic compound and a nitrogen atom-containing organic compound as organic additives and adapted for electrolytic plating substrates having through-holes, blind via holes, posts or the like when a specific polymer compound is used as the nitrogen atom-containing organic compound, high-speed copper electrolytic plating can be satisfactorily carried out. More specifically, the polymer compound used as the nitrogen atom-containing organic compound is obtained by a two-stage reaction comprising reacting one mole of morpholine with two moles of epichlorohydrin in an acidic aqueous solution to obtain a reaction product and further reacting one to two moles, relative to one mole of the morpholine, of imidazole with the reaction product. This polymer compound effectively functions as a leveler, especially, in the copper electrolytic plating bath at a temperature as high as 35° C. or over. As a consequence, high-speed copper electrolytic plating can be carried out on substrates having through-holes, blind via holes, posts or the like formed therein while keeping a throwing powder and ensuring the physical properties of the deposit.

Accordingly, the invention provides the following copper electrolytic plating bath and method.

-   [1] A copper electrolytic plating bath comprising copper sulfate in     an amount of 50 to 250 g/liter calculated as copper sulfate     pentahydrate, 20 to 200 g/liter of sulfuric acid, and 20 to 150     mg/liter of chloride ions, and a sulfur atom-containing organic     compound and a nitrogen atom-containing organic compound serving as     organic additives, said nitrogen atom-containing organic compound     being a nitrogen atom-containing polymer compound obtained by a     two-stage reaction comprising reacting one mole of morpholine with     two moles of epichlorohydrin in an acidic aqueous solution to obtain     a reaction product and further reacting one to two moles, relative     to one mole of the morpholine, of imidazole with the reaction     product. -   [2] The copper electrolytic plating bath as defined in [1], wherein     said nitrogen atom-containing polymer compound is present in an     amount of 1 to 1,000 mg/liter. -   [3] The copper electrolytic plating bath as defined in [1], wherein     said sulfur atom-containing organic compound is a compound selected     from sulfur atom-containing organic compounds represented by the     following formulas (1) to (4) and is present in an amount of 0.001     to 100 mg/liter

wherein R₁, R₂ and R₃ independently represent an alkyl group having 1 to 5 carbon atoms, M represents a hydrogen atom or an alkali metal, a is an integer of 1 to 8, and b, c and d are, respectively, 0 or 1.

-   [4] A copper electrolytic plating method comprising plating an     article to be plated with the copper electrolytic plating bath     defined in any one of [1] to [3] at a temperature of 30 to 50° C. -   [5] The copper electrolytic plating method as defined in [4],     wherein the article to be plated is a substrate having     through-holes, blind via holes or posts. -   [6] The copper electrolytic plating method as defined in [5],     wherein the through-hole has a diameter of 0.05 to 2.0 mm, a height     of 0.01 to 2.0 mm and an aspect ratio of 0.1 to 10, the blind via     hole has a diameter of 20 to 300 μm and a height of 20 to 150 μm,     and the post has a diameter of 30 to 300 μm, a height of 25 to 200     μm and an aspect ratio of 0.2 to 3.

ADVANTAGEOUS EFFECTS OF INVENTION

The nitrogen atom-containing polymer compound used as an organic additive and serving as a leveler does not change in quality when a plating temperature is elevated and is able to keep a good balance between the promoter effect and the inhibitor effect ascribed to the organic additive present in the plating bath under temperature-elevated conditions. Hence, the copper electrolytic plating bath of the invention allows a throwing power relative to through-holes or blind via holes and physical properties of the deposit to be kept when the plating temperature is elevated. Using the copper electrolytic plating bath of the invention, high-speed plating can be performed even under weak agitation, such as air agitation, which is milder than jet flow. In the past, high-speed plating has been hitherto carried out by application of plating temperature and cathode current density conditions essentially requiring vigorous agitation such as of jet flow.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(A) and 1(B) are, respectively, a sectional view of part of a substrate illustrating a portion at which a thickness of the deposit is measured for evaluating a throwing power in Examples and Comparative Examples wherein FIG. 1(A) is a sectional view of a through-hole and FIG. 1(B) is a sectional view of a blind via hole; and

FIG. 2 is a schematic view showing a shape and a size of a test piece used for measurement of physical properties of the deposit in Examples and Comparative Examples.

DESCRIPTION OF EMBODIMENTS

Now, the invention is described in more detail.

The copper electrolytic plating bath of the invention contains copper sulfate, sulfuric acid and chloride ions. Copper sulfate is contained as copper sulfate pentahydrate in an amount of 50 to 250 g/liter, preferably 100 to 200 g/liter, sulfuric acid is contained in an amount of 20 to 200 g/liter, preferably 50 to 200 g/liter, and the chloride ion is contained in an amount of 20 to 150 mg/liter, preferably 30 to 100 mg/liter.

The copper electrolytic plating bath of the invention further contains a sulfur atom-containing organic compound and a nitrogen atom-containing organic compound. The sulfur atom-containing organic compounds may be known sulfur atom-containing organic compounds ordinarily used for copper electrolytic plating of through-holes or blind via holes. More particularly, there can be used sulfur atom-containing organic compounds of the following formulas (1) to (4):

wherein R₁, R₂ and R₃ independently represent an alkyl group having 1 to 5 carbon atoms, M represents a hydrogen atom or an alkali metal, a is an integer of 1 to 8, and b, c and d are, respectively, 0 or 1. The concentration of the compound in the copper electrolytic plating bath is generally at 0.001 to 100 mg/liter.

The nitrogen atom-containing organic compound used in the copper plating bath of the invention is a polymer compound, which is obtained by a two-stage reaction including reacting one mole of morpholine with two moles of epichlorohydrin in an acidic aqueous solution to obtain a reaction product and further reacting one to two moles, relative to one mole of the morpholine, of imidazole with the reaction product. This nitrogen-containing polymer compound serves as a so-called leveler and does not undergo quality change when the plating temperature is elevated, for example, to 30° C. or over, particularly, to 35 to 50° C. Under high temperature conditions, the polymer compound is able to keep a good balance between the promoter effect and the inhibitor effect ascribed to the organic additives contained in the plating bath. In the course of copper electrolytic plating on a non-flat portion formed on a substrate such as through-holes or blind via holes or on a non-flat portion formed such as with a resist film upon formation of posts (bumps), the nitrogen-containing polymer compound serves as an effective leveler capable of keeping a throwing power and physical properties of the deposit as they are when the plating temperature is elevated.

This nitrogen atom-containing polymer compound is known as CAS No. 109882-76-0 and is considered to be a polymer compound having a polyether structure. This polymer compound is one obtained by the two-stage reaction including a first stage of reaction between one mole of morpholine and two moles of epichlorohydrin and a second stage of reaction wherein one to two moles, preferably about two moles and more preferably 1.8 to two moles of imidazole is added to the reaction product of the first stage to provide a polymer compound.

More particularly, for example, one mole of morpholine is dissolved in about 375 ml of distilled water, which is adjusted in pH to 5.5 by means of HCl. Two moles of epichlorohydrin are dropped in the solution at a reaction temperature of about 50° C., followed by keeping at 40° C. to 50° C. until free epichlorohydrin is not detected (first stage). Next, one mole of imidazole is added to the reaction product obtained in the first stage, to which 50 g of NaOH dissolved in 125 ml of water is added, followed by reaction at 55° C. to 60° C. for 6 hours (second stage). The water is further added to the obtained solution, whereby the resultant solution of which the total amount is one litter can be used. As a commercial product of such a polymer compound, mention is made of Ralu (registered trademark) Plate MOME (made by Raschig GmbH) and the like.

The concentration of the nitrogen atom-containing polymer compound in the copper electrolytic plating bath is at 1 to 1,000 mg/liter, preferably 10 to 500 mg/liter.

The copper electrolytic plating bath of the invention may further comprise oxygen-containing organic compounds including polyether organic additives such as polyethylene glycol used in copper electrolytic plating of through-holes or blind via holes. The concentration of the oxygen-containing organic compound in the copper electrolytic plating bath is preferably at 0.001 to 5,000 mg/liter. It will be noted that polyethylene glycol useful in the invention is one having a molecular weight of 200 to 200,000. The molecular weight in this case is measured according to a method described in Japanese Pharmacopoeia.

In copper electrolytic plating using the copper electrolytic plating bath of the invention, the conventional plating conditions are applicable. Especially, when employing a plating temperature of not lower than 35° C., preferably 35° C. to 50° C. and a cathode current density of not less than 5 A/dm², preferably 5 to 20 A/dm², a more stable throwing power and better characteristics of deposit than those obtained in the conventional copper electrolytic plating can be attained.

The anode used is preferably an insoluble anode. For example, there can be used an anode wherein platinum, iridium oxide or the like is coated on titanium. Various types of agitation created by known agitation means may be used including, for example, jet flow agitation or circulation agitation made by a pump, air agitation made by an air pump, and mechanical agitation made by a paddle, cathode locking means or the like.

The copper electrolytic plating using the copper electrolytic plating bath of the invention is particularly suited for copper electrolytic plating of articles to be plated such as printed boards having a non-flat portion formed on or in a substrate such as through-holes or blind via holes, or a non-flat portion formed by a resist film upon formation of posts (bumps) or the like. The copper electrolytic plating is especially effective for the case of forming the deposit on inner surfaces of blind via holes including a bottom face and side faces of the blind via holes (the case does not apply via filling plating where the blind via holes are filled by copper plating).

The invention is suited for copper electrolytic plating of substrates having through-holes or blind via holes having a large aspect ratio (AR). For instance, the invention is effective for high-speed plating of through-holes having a diameter of 0.05 to 2.0 mm, preferably 0.1 to 1.0 mm, a sheet thickness (height) of 0.01 to 2.0 mm, preferably 0.05 to 1.6 mm, and an aspect ratio (AR), i.e. height/diameter, of 0.1 to 10, preferably 0.1 to 5.0, and also of blind via holes having a diameter of 20 to 300 μm, preferably 30 to 200 μm, a height (depth) of 20 to 150 μm, preferably 40 to 100 μm, and an aspect ratio (AR), i.e. height/diameter, of 0.2 to 1.5, preferably 0.4 to 1.0.

When posts (bumps) are formed by plating, there are mainly used two methods including a method wherein an electroplated copper layer is formed on the surface of an article on which posts (bumps) are to be formed and the post (bump)-formed portion is protected with an etching resist film, followed by etching the portion not covered with the resist film and thereafter removing the resist film, and a method wherein a plating resist pattern is formed by a resist film on the surface of an article so that posts (bumps) to be formed are opened, and copper plating is carried out on this opening portion, followed by removing the resist film. In the former method, speeding up of the copper plating is possible. However, where posts (bumps) having a large aspect ratio (AR) are formed, the outer periphery of the posts (bumps) having been formed is seriously corroded at the central portion along the height thereof into a bobbin-shaped one, with the attendant problem that the sectional verticality lowers. When the posts (bumps) formed are high a problem is arisen in that it takes a long time for etching.

Where posts (bumps) are formed according to the copper electrolytic plating of the invention, it is preferred to use the latter method making use of a plating resist film. More particularly, the copper electrolytic plating of the invention is effective for high-speed plating of posts (bumps) having a large aspect ratio (AE), e.g. a post (bump) having a diameter of 30 to 300 μm, preferably 50 to 200 μm, a height (resist film height) of 25 to 200 μm, preferably 30 to 150 μm, and an aspect ratio (AR) of 0.2 to 3, preferably 0.3 to 2. In this case, it will be noted that the plating is such that the deposit is filled in a recessed portion formed at an opening of the plating resist.

EXAMPLES

Examples and Comparative Examples are shown to more particularly describe the invention, which should not be construed as limited to the following Examples.

Examples 1 to 4 and Comparative Examples 1 to 3

Using a laminated substrate having through-holes (of four types) or blind via holes (of two types) indicated in Table 2, copper electrolytic plating baths of the following formulations were used to form electroplated copper layers in the through-holes or blind via holes under the following plating conditions. It will be noted that the copper electrolytic plating was carried out in such a way that a known pretreatment was conducted at a portion where the copper deposit is to be formed, on which an electroless copper film (with a thickness of 0.3 μm) was formed as an underlying layer, followed by copper electrolytic plating.

<Copper Electrolytic Plating Bath>

-   -   Copper sulfate pentahydrate: 150 g/liter     -   Sulfuric acid: 150 g/liter     -   Chloride ion: 50 mg/liter     -   Organic additives: indicated in Table 1

<Plating Conditions>

-   -   Cathode current density: 15 ASD (A/dm²)     -   Temperature: 40° C.     -   Plating time: 8 minutes (corresponding to a copper layer         thickness of 26 μm)     -   Agitation: Slightly strong air agitation

TABLE 1 Organic Example Comparative Example additives 1 2 3 4 1 2 3 SPS 15 15 15 15 15 3.0 3.0 (mg/liter) PEG#6000 300 0 300 0 300 300 300 (mg/liter) Leveler Polymer compound 1 PAS-A-5 JGB Nil (mg/liter) 50 50 10 500 50 1.0 Nil SPS: Disodium bis (3-sulfopropyl) disulfide disodium salt PEG#6000: Polyethylene glycol 6000 (made by Wako Pure Chemical Industries, Ltd.) Polymer compound 1: Ralu (trademark) Plate MOME (made by Raschig GmbH) PAS-A-5: Copolymer of diallyldialkylammonium and sulfur dioxide (made by Nitto Boseki Co., Ltd., and having an average molecular weight of 4,000) JGB: Janus green black

It will be noted that the amounts of PAS-A-5 and JGB were, respectively, set from an additive concentration sufficient to give a gloss in the highest electric potential region when determined by Hull cell test.

The outer appearance after copper electrolytic plating was visually observed and the throwing power (TP) was evaluated in the following way. The results are shown in Table 2.

[Evaluation of Throwing Power (TP)] (1) Through-Hole (TH)

The thickness of the copper layer at portions A to F indicated in FIG. 1(A) was measured, followed by evaluation in terms of a ratio (%) calculated according to the following equation. It should be noted that as to E and F, the thickness at the central portions of the through-hole indicated at E₁ and F₁ was measured for Examples 1 to 4 and Comparative Examples 1, 3 and the thickness at upper end portion of the through-hole indicated at E₂, F₂ was measured for Comparative Example 2.

TP(%)=2×(E+F)/(A+B+C+D)×100

E=E₁ or E₂ and F=F₁ or F₂. (2) Blind Via Hole

The thickness of the copper layer at portions A to C indicated in FIG. 1(B) was measured, followed by evaluating in terms of a ratio (%) calculated by the following equation.

TP(%)=2×C/(A+B)×100

In FIGS. 1(A) and 1(B), indicated by 1 is a substrate (insulating layer), by 2 is laminated copper, by 3 is an electroless plated copper layer, by 4 is an electroplated copper layer, by t is a through-hole, and by v is a blind via hole.

TABLE 2 Comparative Example Example 2 3 1 2 3 4 1 Partially Partially Appearance Glossy Glossy Glossy Glossy Glossy uneven scorched TP Through-hole (TH) Sheet thickness Hole diameter (mm t) (mm φ) 0.10 0.10 98% 99% 97% 100%  103%  32% 148%  0.20 0.10 97% 98% 97% 99% 101%  35% 111%  1.6 0.6 70% 68% 67% 69% 65% 35% 42% 1.6 0.8 75% 73% 72% 76% 69% 38% 45% Blind via hole (Via) Depth Hole diameter (μm d) (μm φ) 85 150 74% 75% 73% 75% 53% 37% 21% 85 125 72% 72% 70% 71% 35% 41% 16%

It will be noted that in Comparative Example 2, the thickness of the copper layer was smallest at the corner portion of the opening side of the blind via hole, and except for this, the thickness of the copper layer was smallest at the corner portion of the bottom side.

Through-Hole Examples 1 to 4, Comparative Example 1

-   -   With the case where a substrate thickness was small (or a         through-hole length was short), current concentration at the         inside of the through-holes was suppressed, so that the copper         layer thickness inside the through-holes was substantially the         same as on the surface and thus, the throwing power was at about         100%. When the substrate thickness was thick (or the         through-hole length was long), the lowering of current throwing         power inside the through-holes was small and hence, the throwing         powder was suppressed from degrading.

Comparative Example 2

-   -   The leveler suppressed deposition at corner portions of the         through-holes, resulting in a small thickness.

Comparative Example 3

-   -   When the substrate thickness was small (the through-hole length         was short), the current concentrated at the through-hole         portion, rendering the copper layer thickness inside the         through-holes thick, so that the throwing power was far over         100%. On the other hand, when the substrate thickness was large         (or the through-hole length was long), the current did not run         throughout the inside of the through-holes, so that the copper         layer thickness at the central portion of the through-holes         became small, thereby worsening the throwing power.

Blind Via Hole Examples 1 to 4

-   -   Copper deposition on the surface was suppressed owing to a         proper leveling effect and the current ran round the inside of         the blind via holes. The suppressing effect at the corner         portion of the bottom side of the blind via holes was weak and         thus, the current also ran toward the corner portions at the         blind via hole bottom side.

Comparative Example 1

-   -   The leveling effect was weak, and the throwing power was poor at         the corner portion of the blind via hole bottom side toward         which the current was unlikely to run.

Comparative Example 2

-   -   The leveling effect was too strong and thus, the leveler acted         to suppress deposition at the corner portion of the opening side         of the blind via holes, resulting in thin film.

Comparative Example 3

-   -   Because of the absence of a leveler, throwing power at the         corner portion of the blind via hole bottom side, round which         the current was unlikely to run, was very poor.

The copper electrolytic plating baths of Examples 1 to 4 and Comparative Examples 1 to 3 were used to evaluate physical properties of the copper layers according to the following procedures.

[Evaluation of Physical Properties of Copper Layers]

A SUS sheet was subjected to the following pretreatment and an electroplated copper layer was formed on the SUS sheet by the use of the above copper electrolytic plating baths under the following plating conditions. Moreover, after subjecting to the following aftertreatment, a foil-shaped plated layer was peeled off from the SUS sheet. This plated film (layer) was subjected to evaluation of tensile strength and percentage elongation according to the following methods.

<Pretreatment>

-   -   (1) Acidic cleaner treatment         -   (MSC-3-A, made by Uyemura & Co., Ltd.)     -   (2) Hot water washing     -   (3) Water washing     -   (4) Acid washing     -   (5) Water washing

<Plating Conditions>

-   -   Cathode current density: 15 ASD (A/dm²)     -   Temperature: 40° C.     -   Plating time: 15 minutes (corresponding to a copper layer         thickness of 50 μm)     -   Agitation: Slightly strong air agitation

<Aftertreatment>

-   -   (1) Water washing     -   (2) Discoloration prevention         -   (AT-21, made by Uyemura & Co., Ltd.)     -   (3) Water washing     -   (4) Drying

<Measurement of Tensile Strength and Percentage Elongation>

The copper film prepared above was punched out into a dumbbell-shaped test piece with the sizes indicated in FIG. 2, and the percentage elongation and tensile strength before the film was broken down under conditions of a chuck distance of 40 mm and a pulling rate of 4 mm/minute were evaluated by calculation from the following equations.

T[kgf/mm² ]=F[kgf]/(10[mm]×d[mm])

wherein T=tensile strength, F=maximum tensile stress, and d=film thickness at a central portion of test piece.

E[%]=ΔL[mm]/20[mm]

wherein E=percentage elongation, and ΔL=an elongated length before breakage of film.

TABLE 3 Example Comparative Example 1 2 3 4 1 2 3 Tensile Strength 32 33 33 32 34 40 34 (kgf/mm²) Percentage 29 28 28 30 26 15 22 elongation (%)

Examples 5 to 8 and Comparative Examples 4 to 6

Using a laminated substrate wherein a recessed portion having a diameter of 80 μm and a height (depth) of 100 μm was formed on a surface thereof by means of a plating resist film, copper electrolytic plating baths indicated in Table 1 were used to subject the recessed portion, at which posts were to be formed on the laminated substrate, to copper electrolytic plating under the following conditions. It will be noted that the portion to be formed with electrolytic plating copper layer was preliminarily subjected to known pretreatment, followed by forming an electroless copper layer with a thickness of 0.3 μm as an underlying layer and subjecting to copper electrolytic plating.

<Plating Conditions>

-   -   Cathode current density: 10 ASD (A/dm²)     -   Temperature: 35° C.     -   Plating time: 36 minutes (corresponding to a post height of 80         μm)     -   Agitation: slightly strong air agitation

The upper face shape of the posts after copper electrolytic plating was evaluated in respect of the longitudinal section of the posts (i.e. a section along the height). The maximum and minimum values of the post height were measured and a difference therebetween was calculated. The results are shown in Table 4.

TABLE 4 Example Comparative Example 5 6 7 8 4 5 6 Differ- 3.2 3.3 3.5 3.2 13 56 42 ence in post height (μm) Upper Sub- Sub- Sub- Sub- Slight- Slight- Pro- face stan- stan- stan- stan- ly pro- ly re- tru- shape tially tially tially tially truded cessed ded flat flat flat flat

Examples 5 to 8

-   -   Based on the proper leveling effect, there could be obtained         substantially flat posts although the copper layer was slightly         thin at end portion.

Comparative Example 4

-   -   The leveling effect was too weak, so that the copper layer at         the end portion was thin.

Comparative Example 5

-   -   The leveling effect was too strong, so that the copper layer at         the end portion was extremely thick.

Comparative Example 6

-   -   Because of no leveling effect, the copper layer at the end         portion became too thin.

Japanese Patent Application No. 2009-238460 is incorporated herein by reference.

Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims. 

1. A copper electrolytic plating bath comprising copper sulfate in an amount of 50 to 250 g/liter calculated as copper sulfate pentahydrate, 20 to 200 g/liter of sulfuric acid, and 20 to 150 mg/liter of chloride ions, and a sulfur atom-containing organic compound and a nitrogen atom-containing organic compound serving as organic additives, said nitrogen atom-containing organic compound being a nitrogen atom-containing polymer compound obtained by a two-stage reaction comprising reacting one mole of morpholine with two moles of epichlorohydrin in an acidic aqueous solution to obtain a reaction product and further reacting one to two moles, relative to one mole of the morpholine, of imidazole with the reaction product.
 2. The copper electrolytic plating bath as defined in claim 1, wherein said nitrogen atom-containing polymer compound is present in an amount of 1 to 1,000 mg/liter.
 3. The copper electrolytic plating bath as defined in claim 1, wherein said sulfur atom-containing organic compound is a compound selected from sulfur atom-containing organic compounds represented by the following formulas (1) to (4) and is present in an amount of 0.001 to 100 mg/liter

wherein R₁, R₂ and R₃ independently represent an alkyl group having 1 to 5 carbon atoms, M represents a hydrogen atom or an alkali metal, a is an integer of 1 to 8, and b, c and d are, respectively, 0 or
 1. 4. A copper electrolytic plating method comprising plating an article to be plated with the copper electrolytic plating bath defined in any one of claims 1 to 3 at a temperature of 30 to 50° C.
 5. The copper electrolytic plating method as defined in claim 4, wherein the article to be plated is a substrate having through-holes, blind via holes or posts.
 6. The copper electrolytic plating method as defined in claim 5, wherein the through-hole has a diameter of 0.05 to 2.0 mm, a height of 0.01 to 2.0 mm and an aspect ratio of 0.1 to 10, the blind via hole has a diameter of 20 to 300 μm and a height of 20 to 150 μm, and the post has a diameter of 30 to 300 μm, a height of 25 to 200 μm and an aspect ratio of 0.2 to
 3. 